1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) technology, more particularly, to a compensation system and a liquid crystal display apparatus for a liquid crystal panel.
2. Description of the Related Art
With the development of technology, a liquid crystal display apparatus has become the mainstream of the display apparatus. However, when the viewing angles of the liquid crystal display apparatus are enlarged, the contrast of pictures is reduced and the sharpness is lowered. The reason lies in that the birefringence of the liquid crystal molecules of the liquid crystal layer changes as a result of the change of the viewing angle. Light leakage of dark images is effectively reduced if a wide view film (WVF) is utilized. Hence, the contrast of pictures is significantly increased within a certain range of viewing angles. A retardation film, usually applied to a vertical alignment (VA) mode, mainly comprises a single-layered biaxial retardation film or a double-layered biaxial retardation film. For different optical path differences of liquid crystals (Δn×d), the minimum light leakage in dark mode is achieved by utilizing retardation films having different retardation values. If an unmatched retardation film is utilized with the liquid crystal display apparatus, not only does light leakage in dark mode occur at large viewing angles but also the contrast and sharpness at large viewing angles are affected.
Please refer to FIG. 1 and FIG. 2, FIG. 1 shows a simulation of a distribution of light leakage in dark mode after being compensated by a conventional double-layered biaxial retardation film. FIG. 2 shows a simulation of a distribution of contrast over all viewing angles after being compensated by the conventional double-layered biaxial retardation film. The optical path difference of liquid crystal Δn×d is set at 342.8 nm. The in-plane retardation value of the double-layered biaxial retardation films Ro is 70 nm, and the out-of-plane retardation value in a thickness direction of the double-layered biaxial retardation film Rth is 160 nm. As can be seen from FIG. 1 and FIG. 2, under these circumstances there is severe light leakage problem in areas at azimuth angles between 30 degrees and 60 degrees, 120 degrees and 150 degrees, 210 degrees and 240 degrees, and 300 degrees and 330 degrees even after being compensated by the double-layered biaxial retardation film. As a result, the contrast along these viewing angles is lowered.
Therefore, it is very important to provide a compensation system and a liquid crystal display apparatus used for a liquid crystal panel to resolve the above-mentioned problem.